Two-Step Carbonization as a Method of Enhancing Catalytic Properties of Hemoglobin at the Fuel Cell Cathode

Abstract

Recently, there has been increased demand for a polymer electrolyte fuel cell (PEFC) that functions efficiently with far less or no Pt. In this study, the catalyst for the O 2 reduction at the cathode was formed by carbonizing hemoglobin, which could be abundantly and inexpensively obtained. A substantial enhancement of catalytic properties was achieved by a change in the carbonization process from one step to two steps. The PEFC using the carbonized hemoglobin formed in the modified carbonization process generated a high power comparable to those formed using a Pt-free cathode as reported already. The power densities of 0.11 and 0.16 W cm -2 were attained using H 2 and O 2 gases at atmospheric pressure (H 2 and O 2 partial pressures, 54 kPa) and using pressurized gases (H 2 and O 2 partial pressures, 254 kPa), respectively. The carbonization modification reduced the Fe valence state from 3+ to 2+ in the carbonized hemoglobin, which was demonstrated by X-ray photoelectron spectroscopy. The catalysis enhancement was probably attributed to the increase in Fe(II), which was required as an O 2 bonding site in the first step of the multistep cathodic O 2 reduction process.

Hemoglobin Pyropolymer Used as a Precursor of a Noble-Metal-Free Fuel Cell Cathode Catalyst

“…We previously reported that the micropore development in the catalyst exposes the active site to the micropore surface and increases the number of active sites and, consequently, the activity. 11,12 In this study, the specific surface area increased with a decrease in the heat-treatment temperature of the hemoglobin pyropolymer; therefore, this was the determining factor for the increase in the activity. The increases in the specific surface area and the mean pore diameter possessed an additional effect for enhancing the activity due to the increase in the availability of O 2 molecules for the individual active sites inside the micropore of the catalyst.…”

Fe/N/C non-precious catalysts for PEM fuel cells: Influence of the structural parameters of pristine commercial carbon blacks on their activity for oxygen reduction

“…Several groups have since developed Fe/N/C and Co/N/C electrocatalysts and their work has been summarized in a recent review [3]. Since this review was written, several researchers (including our group) have continued to follow Yeager's steps and obtained Fe and Co-based catalysts for the oxygen reduction reaction (ORR) that are active in fuel cell conditions [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22].…”

A Highly Nanoporous Nitrogen-Doped Carbon Microfiber Derived from Bioresource as a New Kind of ORR Electrocatalyst

“…The use of natural biomass (e.g., soybean [19], silk fibroin [20], kidney bean [21], and hemoglobin [22]) and animal biowastes (e.g., fish scale [23] and animal blood [24]) as a direct precursor or the nitrogen source of catalytically ORR-active sites was thought as an effective pathway to fabricate the doped-carbon catalysts. More recently, Li et al also synthesized a doped carbon-based ORR catalyst with three-dimensional porous network via using hemin biomaterial as a single-source precursor and using self-assembled sodium chloride crystallines as the template [25].…”